Face mask valve



FIG. 1 is a top plan view of a face mask valve showing my design and how it is attached to a face mask;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a side elevational view thereof, the opposite side elevational view being a mirror image of that shown; and,

FIG. 4 is top perspective view thereof.

The broken lines showing of a face mask are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a face mask valve, as shown and described. 